Idiopathic facial palsy or Bell's palsy remains the most common cause of acute facial paralysis, affecting one in every 5,000 persons. Although the cause of this disorder remains unknown, accumulating evidence supports a viral inflammatory immune mechanism. Nevertheless, the diagnosis of Bell's palsy requires the elimination of all other possible etiologic factors, including tumors, infections and trauma.
Bell's palsy is a self-limiting, non-progressive, non-life-threatening, and in most cases, spontaneously remitting disorder. It is without age or racial predilection and has a three times higher incidence among pregnant women, particularly those in their third trimester, than in non-pregnant women of the same age group. Unfortunately, at this time Bell's palsy can neither be prevented nor cured.
The frustration of the clinician managing patients with this disorder of unknown cause is compounded by the fact that no treatment (either medical or surgical) has been proven by clinical trials to favorably influence the course of Bell's palsy.
CLINICAL FEATURES
Idiopathic facial paralysis is characterized by a viral prodrome (60%) which is accompanied by pain around the ear (50%), facial numbness (40%), changes in taste (15%), and numbness of the tongue (20%). The onset of paralysis is usually sudden and unilateral. A positive family history has been found in 14% of the patients with Bell's palsy, and in 12% of patients the syndrome has recurred.
NATURAL HISTORY
Pietersen studied the natural history of Bell's palsy and found that in 84% of cases recovery of facial function was satisfactory: 71% recovered without any sequelae and 13% had defects that were barely noticeable. The remaining 16% of patients had incomplete recovery of facial function, but sequelae were crippling in only 4%. However, there was not a single patient who did not have some recovery.
Of those with a history of recurrence, the alternate side of the face was involved in 64%, while in the remaining 36%, the same side of the face was involved.
EVALUATION
When evaluating patients with facial paralysis, it must be emphasized that Bell's palsy is a diagnosis of exclusion, reserved for cases in which all other known causes of acute facial paralysis have been ruled out.
Diagnostic clues are obtained from a carefully taken history, physical examination and special testing. Bell's palsy can be ruled out if one of the following is present: sign of tumor, bilateral simultaneous palsy, herpes zoster cephalicus (Ramsay Hunt's syndrome), progressive involvement of multiple motor cranial nerves, history and findings of trauma, ear infection, sign of central nervous system lesion, facial palsy noted at birth, or a triad of infectious mononucleosis (fever, sore throat and cervical lymphadenopathy).
In addition to a history and physical examination, special testing should include evaluation of tearing, hearing, stapes reflex, and electrical testing employing maximum stimulation or evoked electromyography. Electrical tests are most useful when given within the first 10 days following onset and may be a helpful predictor of outcome. For example, if the patient responds to electrical stimulation within the first 10 days, there is an 80% chance of satisfactory recovery. If, however, the response to electrical stimulation is lost within the first 5 days following onset, there is only a 20% chance of satisfactory recovery. Moreover, patients with the most favorable outcomes begin to show return of function within 3-6 weeks. Those with less favorable outcomes may not show signs of recovery for 2-4 months. In some cases, recovery may not begin for 6-8 months.
TREATMENT OF BELL'S PALSY
Management of acute facial paralysis requires first identifying the cause, determining the prognosis, and then choosing, when necessary, the best therapeutic approach.
Fortunately for the majority of patients with Bell's palsy, the prognosis is favorable. Indeed, 85% of patients will recover satisfactory degrees of facial function without treatment. Unfortunately, for those with less favorable outcomes, there are no treatment modalities currently available that have been shown to favorably influence the course of Bell's palsy.
STEROID-SURGERY CONTROVERSY
Two current forms of therapy include corticosteroids and surgery. Some investigators feel that corticosteroids have some value in the treatment of bell's palsy if administered within the first few days after onset. The benefit of facial nerve surgical decompression has not been established for Bell's palsy. In fact, among the advocates of surgical management for Bell's palsy there has been lack of agreement regarding the segment of facial nerve to be decompressed, the best surgical approach, the timing of surgery, the indications for surgery, and finally, the reporting of results. Surgery cannot be performed without risk to hearing, balance, the facial nerve or life itself.
However, in certain situations, surgery may be indicated. For example, facial paralysis due to an ongoing process, such as chronic ear disease with or without cholesteatoma, can only be relieved by eradicating the primary process. In addition, there are two situations where surgery is absolutely indicated in managing facial nerve disorders: facial nerve transection and tumor infiltration. Further, there are times when a diagnosis of nerve transection or tumor infiltration can only be established by surgical exploration. This is true when either the temporal bone has been fractured or a tumor is suspected.
In acute facial paralysis following trauma due to fracture of the temporal bone, exploration should be performed - provided there is sudden, complete paralysis, loss of response to the electrical stimulation by the 5th day after onset, and disruption through the fallopian canal noted by CT scanning. Surgery should be performed as soon as the patient's general condition permits. In the absence of one or more of these findings, spontaneous recovery should be noted within 4-6 months.
Tumor
Signs suggesting that a tumor is causing facial paralysis include: sudden and complete onset, loss of response to evoked electromyography prior to the 5th day of onset, recurrent on the same side palsy, slowly progressive weakness beyond 3 weeks, progressive facial numbness accompanied by persistent weakness, facial twitching with weakness, no recovery after 6 months, other simultaneous or progressive cranial nerve motor deficits, involvement of single or multiple facial nerve branches with sparing of the rest, mass between the mastoid tip and the mandible, and a history or discovery of a malignancy.
Patients in whom a tumor is suspected should be studied by CT scanning of the temporal bone. Investigators should evaluate the course of the facial nerve throughout the fallopian canal, as well as the area of the cerebellopontine angle and internal auditory canal. The region of the stylomastoid foramen, skull base and parotid should be included in this radiographic study. Patients believed to have a tumor should be considered for exploration.
MEDICAL MANAGEMENT
Until the steroid-surgery controversy is resolved, the management of Bell's palsy must be directed toward relieving mental depression, protecting the cornea from breakdown, and general support until satisfactory recovery of facial functional has occurred.
Among the patient's medical requirements, protective and preventive eye care takes priority. Because paralysis may prevent normal blinking, the patient should voluntarily close the involved eyelid 2-4 times a minute, or whenever the eye feels irritated or burns. In addition, eye drops (Tears Naturale 2 every hour) should be used during the day and ointment (Lacrilube S.O.P) at night. A moisture chamber should be worn over the eye while outdoors or if the eye becomes irritated.
Surgery to reanimate the paralyzed eyelids with gold weights or springs combined with lower lid shortening should be considered if medical treatment if ineffective.
The deformity associated with facial paralysis can cause patients to become depressed. Patients should be openly informed of their prognosis, and when recovery is not expected for 2-4 months, they should be supported sympathetically. Drug therapy is a poor substitute for counseling and should be used as a last resort.
Approximately half the patients with Bell's palsy and almost all patients with herpes zoster cephalicus experience pain associated with their condition. In most cases, the pain can be controlled with a non-narcotic medication, although in rare instances narcotics may be required. Pain due to Bell's palsy usually subsides by the 10th day after onset. However, pain caused by herpes zoster cephalicus may persist intermittently for as long as 3 months.
CONCLUSION
Because of the lack of evidence supporting the benefits of either steroid therapy or mastoid surgery in the routine treatment of Bell's palsy, we must wait for a multicenter study capable of obtaining statistically significant data based on sufficient numbers of patients.
Middle fossa surgery, as suggested by Fisch, to open the proximal meatal segment, is also being studied and should be considered investigational at present.
Until more definitive results are obtained regarding the value of surgery, the treatment of Bell's palsy must largely be limited to medical management with particular attention to protection of the cornea.
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